Structural Identification of the Vps18 β-Propeller Reveals a Critical Role in the HOPS Complex Stability and Function
Structural Identification of the Vps18 β-Propeller Reveals a Critical Role in the HOPS Complex Stability and Function
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DOI：
10.1074/jbc.m114.602714
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发表时间：
2014-11-28
影响因子：
4.8
通讯作者：
Ungermann, Christian
中科院分区：
文献类型：
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作者：
Behrmann, Heide;Luerick, Anna;Ungermann, Christian
液泡的膜融合是酵母中相当于溶酶体的，需要啤酒花拴系复合体，该复合体由Rab7 GTP酶Ypt7招募。啤酒花为陷阱的组装提供了模板，因此很可能在液泡上的不同位置实现融合。在啤酒花的6个亚基中，有5个亚基的结构域预测与COPII亚基和核孔蛋白有很大的相似性。在这里，我们通过揭示其2.14埃的结构，证明了Vps18确实有一个七叶片的β-螺旋桨作为其N-末端结构域。Vps18的N-末端结构域可以与Vps11的N-末端部分相互作用，也可以与脂质结合。尽管如负染色电子显微镜所示，Vps18 N-末端结构域的缺失并不排除Hop的组装，但该复合体是不稳定的，不能支持体外膜融合。因此，我们得出结论，Vps18的贝塔螺旋桨是啤酒花稳定性和功能所必需的，它可以作为进一步分析啤酒花系留复合体结构的起点。
Membrane fusion at the vacuole, the lysosome equivalent in yeast, requires the HOPS tethering complex, which is recruited by the Rab7 GTPase Ypt7. HOPS provides a template for the assembly of SNAREs and thus likely confers fusion at a distinct position on vacuoles. Five of the six subunits in HOPS have a similar domain prediction with strong similarity to COPII subunits and nuclear porins. Here, we show that Vps18 indeed has a seven-bladed beta-propeller as its N-terminal domain by revealing its structure at 2.14 angstrom. The Vps18 N-terminal domain can interact with the N-terminal part of Vps11 and also binds to lipids. Although deletion of the Vps18 N-terminal domain does not preclude HOPS assembly, as revealed by negative stain electron microscopy, the complex is instable and cannot support membrane fusion in vitro. We thus conclude that the beta-propeller of Vps18 is required for HOPS stability and function and that it can serve as a starting point for further structural analyses of the HOPS tethering complex.